Plotters used for navigational purposes in the prior art, are comprised substantially of a marker or indicator which is displaced along a rectangular set of coordinates x - y, in accordance with the motion or displacement of the vehicle which is traced by the plotter.
To operate these plotters, heretofore, positional information is supplied to the plotter in the form of x - y coordinates for displacing the marker or indicator correspondingly along the rectangular axes of the plotter. Furthermore, the position of the marker or indicator of the plotter, or any point on the trace plotted, is read out from the plotter in terms of x - y coordinates.
In determining the geographical position of a vehicle such as an aircraft during flight, for example, navigational system aids are often used such as Omega or Loran. By communicating with predetermined Omega or Loran stations, the navigator of the aircraft may obtain lines of position which intersect at a point corresponding to the geographical position of the aircraft. After receiving the aircraft's position in terms of Omega or Loran lines of position, the navigator is generally required to convert or translate these lines of position in corresponding x - y coordinates compatible with the form of information acceptable by the plotter. Such conversion of coordinates by the navigator is a tedious and time consuming process, and considerably subject to human error. At the same time, if the conversion of coordinates is carried out with the aid of computers which are connected directly to the plotter for the purpose of reducing the computational time and errors, the interconnection and linkages which are required, are complex, and the computer is required to solve involved equations. As a result, a special purpose navigational computer carried aboard an aircraft for this purpose of providing the conversion among coordinates, is complex in design, costly, and constitutes substantially large and heavy equipment.
Accordingly, it is an object of the present invention to provide a navigational plotter capable of accepting geographical position information directly in terms of Omega or Loran lines of position, and displaying the information on a chart which has x - y coordinates.
Another object of the present invention is to provide a navigational plotter in which the location of a point may be defined in terms of x - y coordinates on a chart, and this location of the point may be read out of the plotter in terms of Omega or Loran systems.
A further object of the present invention is to provide a navigational plotter of the foregoing character which may be operated manually and in conjunction with navigational computers as, for example, dead reckoning computers.
It is a particular object of the present invention to provide a plotter, as described, which is simple in design, particularly accessible for maintenance, and may be manufactured economically.